I am in my mid forties. All my life different walks of people in a wide varieties of settings have come to the same conclusion about me when I try to socialize:"What are smiling bout"? In short, they stare me down and don't understand why I smile.
In my head, I have preconceived ideas about everyone. I don't see people wanting to get along, they want to compete in every endeavor. Sometimes I am shocked when people actually think of me or even use my first name which is an odd-ball name" Kirk". As a boy,(Ages 0-12)my mother was routinely beaten by my father. He still lives today as a selfish hermit on an 120 acre parcel that used to be a dairy farm. My mother vented some on me after her beatings, but she has the "Smiling too Much disorder too". I think she just has it with me though. I have studied her around others and she does not smile so much to them.
In my case, I smile as I communicate with every human I associate with.